The present invention relates to an indexable cutting insert used for cutting machine parts, etc.
More specifically, in the present invention, the indexable cutting insert has a polygonal shape such as a triangle, a quadrangle or the like. Circular nose portions are, respectively, formed at vertexes of the indexable cutting insert. A cutting edge for effecting cutting directly is linearly formed between neighboring ones of the nose portions. A land portion and a dimple are formed inside the cutting edge so as to constitute a chip breaker. Especially, the cutting edge between the neighboring nose portions is linearly inclined upwardly in a direction away from each of the neighboring nose portions. Thus, the dimple having a predetermined shape of a recess is formed adjacent to and inside each of the nose portions so as to be disposed adjacent to the land portion through a chip breaker wall surface, etc. Thus, the indexable cutting insert of the present invention has excellent copying functions having a wide range of applications including rough cutting, medium cutting and finish cutting.
Machined parts are widely used in many fields of industry and machining accuracy of the machined parts has been improved greatly. Recently, there is a keen demand for higher machining accuracy of the machined parts. A majority of machine parts are subjected to rough cutting, medium cutting and finish cutting in many cases. Hence, since the machine parts are subjected to cutting many times, complicated processes and strict accuracy are required for resharpening cutting tools for cutting the machine parts, thereby resulting in rise of production cost of the machine parts. Therefore, in order to obviate such an inconvenience, indexable cutting inserts have been recently used widely. In order to enable the indexable cutting inserts to be used many times, a circular nose portion is provided at each of vertexes of each of the indexable cutting inserts and a cutting edge is provided between neighboring ones of the vertexes. For example, as shown in FIGS. 1 to 3, indexable cutting inserts 1, 1' and 1" shown in FIGS. 1 to 3, respectively and having a triangular or quadrangular shape enabling repeated use are employed. In FIG. 1, the indexable cutting insert 1 has three circular nose portions 2. Three cutting edges 3' are linearly formed between neighboring ones of the nose portions 2. A land portion 5 having a predetermined size is provided inside each of the cutting edges 3' through a chip breaker groove 4. Thus, in the indexable cutting insert 1, since its cross-sectional shape taken along each of the cutting edges 3 is uniform, the indexable cutting insert 1 can be manufactured easily. Furthermore, in the indexable cutting insert 1, since an obstacle is not present in the vicinity of the nose portions 2, cutting can be performed easily by the indexable cutting insert 1. However, the indexable cutting insert 1 is disadvantageous in that it is difficult to perform cutting having variable depth of cut or finish cutting having a small depth of cut by the indexable cutting insert 1.
Meanwhile, in the indexable cutting inserts 1' and 1" shown in FIGS. 2 and 3, respectively, since the cross-sectional shape changes along each of the cutting edges 3 and the land portion 5 or a projection 5' is formed also in the vicinity of each of the nose portions 2 as shown in FIG. 5, chip disposal can be performed in a wider region than the idexable cutting insert 1. However, the indexable cutting inserts 1' and 1" have such drawbacks that the land portion 5 or the projection 5' functioning effectively during finish cutting having a small depth of cut not only increases the cutting resistance during medium cutting or rough cutting but causes clogging of chips, thereby resulting in restriction of region of chip disposal.
Furthermore, there is a known indexable cutting insert in which a dimple 6 is provided adjacent to each of the nose portions in place of the land portion 5 or the projection 5' as shown in FIG. 4. However, in this known indexable cutting insert, the cutting edge becomes sharp excessively and thus, becomes weak. Therefore, the known indexable cutting insert cannot be used for rough cutting. As a result, the known indexable cutting insert is exclusively used for finish cutting and therefore, cannot be versatilely used for cutting.
Accordingly, the prior art indexable cutting inserts referred to above have fundamental patterns shown in FIGS. 4 and 5 and cannot be used for a wide range of cutting including rough cutting, medium cutting and finish cutting, namely, should be restricted, in application, to one of rough cutting, medium cutting and finish cutting.
Meanwhile, in order to increase region of chip disposal of the prior art indexable cutting inserts in which the cutting edges between neighboring ones of the nose portions are used for rough cutting and the cutting edges of the nose portions are used for light cutting such as finish cutting having a small depth of cut and a low feed rate, various improvements have been proposed. For example, in Japanese Utility Model Publication (examined) Nos. 36562/1987 and 32723/1987, projecting ridges are integrally projected from groove walls of a boss surface and a chip breaker groove so as to be symmetrical with respect to a bisector extending from each of vertex portions of the boss surface towards each of the nose portions. In this known indexable cutting insert, region of chip disposal is increased in light cutting but such undesirable phenomenon take place that chips proceeding from the cutting edge during rough cutting collide with the projecting ridges and are bent by the projecting ridges. Thus, the known indexable cutting insert cannot be used for all cutting ranges.
In order to solve this problem, Japanese Utility Model Publication (examined) No. 10883/1988 has proposed an arrangement in which the projecting ridge projecting from a portion of the boss surface confronting the nose portion extends integrally from the groove wall of the boss surface or rise integrally from the chip breaker groove. Furthermore, an arrangement is known in which the projecting ridge is formed stepwise from the boss surface to the nose portion so as to define height therebetween such that capability of chip disposal is increased in cutting ranging from light cutting to rough cutting. However, these known arrangements are primarily designed to increase region of chip disposal in light cutting of the prior art indexable cutting inserts shown in FIGS. 1 to 3. Thus, the known arrangements have such a drawback that at the time of medium cutting for performing a cutting operation approximate to rough cutting, cutting resistance becomes large, thereby resulting in clogging of chips to be discharged.